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Question for Windell RE: LED Throwie Post

bfinleyuibfinleyui
edited October 2012 in Ask an Evil Mad Scientist
Forgive me if I'm completely missing it, but it seems like the comments section of this post has been closed.  

I have a dumb question, I'm not real familiar with electronics and power streams, but if I'm reading this right:

If the forward voltage of the LED is < 3v forward voltage, a resistor is going to bring it back into that 'completely safe, long-lasting' zone?

For reference, i'm planning on using throwies (possibly inside a ping pong ball as a diffuser) inside paper lamps at my wedding, for part of the centerpieces.  Thus, they only need to last about 12 hours, but the heat was the main concern.

So if i were using this purple LED i wouldn't need a resistor, and would still get the life I was hoping for, but using this yellow one, I would likely be better off with a 200ohm resistor in between the LED and battery, correct?

Thanks for your time, bookmarked the blog for future references, above and beyond this issue.

Comments

  • Windell OskayWindell Oskay
    You are correct that the purple LED will not need a resistor, and that the yellow one would be better off with one.   Heat will not be an issue in any case.

    Also, you might be disappointed in the price/performance ratio of those radio shack LEDs. ;)
  • bfinleyuibfinleyui
    Yeah, just using radioshack as a test bed to get the bride (the one in charge) to make a choice (white lights in colored lanterns, or colored lights in white lanterns).  For the actual items, I'll buy them online.  In fact, I believe I'm going to start with this assorted pack from microtivity on amazon, it has the three colors we're interested in, as well as a ton of extras and resistors.

    Last question, (for now)... I could also put a 3-pin slide switch in to use as an on/off button on this, correct?  Rather than have to teach my aunts (who'll be setting up the venue that afternoon) how to make throwies?

    Thanks for the quick response.
  • Windell OskayWindell Oskay
    Yes, you can add a slider switch, but it may be more complexity than it's worth.  Another good method is a "pull to activate" tab-- a piece of plastic that keeps the battery from making initial contact.
  • bfinleyuibfinleyui
    Eh, I've got 9 months to figure it out.  Always good to have a pile of switches around anyway.  

    Thanks again for the quick help, great site, will definitely be plugging it as I write more in my "how to be a groom" type blog.
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